Spark plug



C. A. XARDELL Aug. 3, 1937.

' SPARK PLUG Filed Sept. 24, 1936 Patented Aug. 3, 1937 NlTED STATES ATENT OFFICE 2 Claims.

This invention has for its object to provide spark plugs, suitable for aviation or other engines, which will withstand the intense heat developed by the high tension electrical currents 5 employed in such engines. To this end the improved spark plugs comprise co-operating, borocarbide elements at the sparking ends of the plugs and between which there are narrow spark gaps; as also to provide improved mica non-conducting elements, as will be hereinafter fully set forth.

In the accompanying drawing Fig. 1 is a vertical section of the improved spark plug; Figs. 2 and 3 are detail sections of the non-metallic sparking elements preferably employed, and Fig.

4 is a bottom end view of this plug.

Referring to'the drawing, I2 denotes the screw threaded shell of the plug, which is of a wellknown form, and into which shell a gland nut 03, also of well-known form, is screwed. Passing through a non-conducting core M, of porcelain or other suitable material, is a main electrode I5 of high heat resisting and of high electrical con-. ductivity, this electrode being slightly flared at its lower end, l5, and being threaded at its upper end for the reception of the terminal nutlli. a

Interposed between the nut l6 and the gland nut I3 is a non-conducting element ll composed of thin leaves of mica. This mica element is assembled under a pressure of several tons, thus forcing the mica leaves or washers into perfect contact, and while stillunder pressure this compacted element is coated on its outside with a strong adhesive which will set quickly thus holding the mica leaves or washers under compression until said mica element is assembled in the spark plug. In other words this non-conducting element is a highly compacted mica unit and is not assembled by screwing down the terminal nut, as

usual, which usual practice does not afford sufficient pressure to seal the joints between the mica leaves or washers perfectly.

In the construction shown in the drawing a Y washer I8 is interposed between the terminal nut I6 and the mica element l1; and a washer is also shown interposed between the gland nut l2 and the shell l2.

The main electrode rod I5 is of high heatresisting material, such as chromium, tungsten or a suitable alloy; and this rod is preferably coated with silver which is of a high heat-resisting and high conducting character. Atthe sparking ing character.

end of this main electrode is located a non-metallic conducting sleeve 20 held in place by the flared end l5 of the said main electrode. This sleeve 20 and the non-metallic conducting ring 2i are spaced apart to afiord an annular sparking 5 gap at 22, said sleeve and ring being of borocarbide, which is of high heat-resisting and-high conducting material, non-fusible by the intense heat to which they may be subjected in use. The non-metallic ring M is held in place by spin- 10 ning over the lower end of the shell it, as shown at It".

It will thus be understood that these boro-carbide and non-fusible sparking elements will result in the production of spark plugs of long life under the high heat of combustion in the engine cylinders, and will also result in spark plugs which will avoid the erosion of the ordinary metallic electrodes due to high tension sparking, thus rendering theseplugs particularly suitable for aviation engines; and these plugs will also be eifective when low grades of hydro-carbon are used for fuel.

It will be noted that the spark gap 22 opens into a space 23 between the shell l2 and the core i4, so thatan aspirating action of the gasses during suction, compression and sparking will result, this aspirating action serving to clean the spark gaps, thus contributing to efficient sparking.

While an annular spark gap is shown in the drawing the non-metallic and practically indestructiblesparking elements may comprise sparking points aifording a plurality of sparking gaps, if desired; or the boro-carbide sparking elements may be of any other suitable form.

The invention is not to be understood as being limited to the details shown and described, as variations, within the province of mechanical skill, may be made without departing from the scope of the invention as defined by the claims hereunto appended.

I claim and desire to secure by Letters Patent:-

1. A spark plug comprising spaced-apart borocarbide, sparking elements of a high heat-resist- 45 2. A spark plug according to claim 1 which comprises a main electrode having a flared end and in which one of the bore-carbide sparking ,elements is in the form 01 a sleeve held in place against said main electrode by said flared end.

CHARLES A. mom-n 

